Autistic disorder is one of five pervasive developmental disorders defined in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision DSM-IV-TR (2000). Autistic disorder is a developmental disorder of the human brain that manifests during infancy or childhood and is characterized by behavioral and social abnormalities that appear to be developmentally based (for example, impairments in social interaction and communication). In addition, autism interferes with imagination and the ability to reason. Autism is frequently associated with other disorders such as attention deficit/hyperactivity disorder (AD/HD) and can be associated with psychiatric symptoms such as anxiety and depression. In the last decade, autism diagnoses have increased by 300% to 500% in the United States and many other countries. A means of prevention and treatment is needed for this health crisis that addresses the underlying mechanisms leading to the development of autism versus those that merely address the symptoms.
Pervasive developmental disorders (PDDs) are also part of the Autism Spectrum Disorders (ASDs). PDD is used to categorize children who do not meet the strict criteria for Autistic Disorder but who come close, either by manifesting atypical autism or by nearly meeting the diagnostic criteria in two or three of the key areas. Some of these children meet criteria for the ASD known as Asperger's Disorder (ASP), wherein language capacities are relatively spared compared to children with Autistic Disorder. Others meet criteria for the PDDs known as Childhood Disintegrative Disorder, which begins at a slightly later age than the other ASDs, or Rett's Disorder, which is related to a mutation in a DNA methylation binding protein gene called MeCP2 and usually occurs in girls.
Many children with autism have gastrointestinal (GI) disturbances that affect their quality of life. Although some of these children have been investigated through GI immunopathology, molecular studies are lacking that characterize host gene expression or survey microflora using pyrosequencing methods.